DESCRIPTION: The long-term objective of this research is to deepen our understanding of the adaptive properties and state-dependent plasticity of the brain. It is known that auditory experience can cause global effects by reshaping cortical maps and local effects by transforming receptive field properties of neurons in the primary auditory cortex (AI). The exact form of this plasticity is determined by the task-relevance of the spectral and temporal characteristics of the acoustic stimuli. Recent research indicates that neuronal responses in AI encode not only the acoustic features of the stimulus, but also reflect behavioral state. This supports the hypothesis that AI cells may undergo rapid, short-term and adaptive context-dependent changes of their receptive field properties when the animal engages in a new auditory task with different stimulus feature salience. In the proposed research, ferrets are trained on two or more different auditory tasks, and then physiological recordings will be made from single neurons while the animal switches between these tasks, leading to observable state-dependent adaptive plasticity on a cellular level. Since the changes observed in primary sensory areas such as AI may be the consequence of top-down projections from higher cortical areas, which are not yet defined in the ferret, I will also begin a neuroanatomical study of major projections from the auditory areas of the ectosylvian gyrus in the ferret, focusing on the reciprocal connections with prefrontal cortex. Once these areas have been described, I will then record from auditory responsive areas in the prefrontal cortex of the ferret using the same approach as described above for behavioral physiology in AI. The health relatedness of this research comes from the fundamental insight it may give into brain plasticity which is vital for an understanding of human brain development, such as language acquisition, and adaptive recovery from brain injury. [unreadable] [unreadable]